At least 33 cities across 17 US states have used water testing cheats that potentially conceal dangerous levels of lead, a Guardian investigation launched in the wake of the toxic water crisis in Flint, Michigan, has found.
Of these cities, 21 used the same water testing methods that prompted criminal charges against three government employees in Flint over their role in one of the worst public health disasters in US history.
The crisis that gripped Flint is an extreme case where a cost-cutting decision to divert the citys water supply to a polluted river was compounded by a poor testing regime and delays by environmental officials to respond to the health emergency.
The Guardians investigation demonstrates that similar testing regimes were in place in cities including Chicago, Boston, Philadelphia, Detroit and Milwaukee